iOS 5 will even everything up.
You have done a marvellous job in summarizing everything. Pretty much nailed the review. Good Job.. Now only if Verizon will allow us to have the same iOS which I belive will be once iOS 5 sees the light of the day...
To be honest, the difference in the OSes are more than just minor Safari improvements. 4.3.x also contains numerous Airplay enhancements (the ability to stream Airplay content from 3rd party apps and websites is the major one).
Another issue is that certain apps simply refuse to install of 4.2.x
It is actually becoming more and more of an issue the more time that goes by. iOS 5 should rectify this problem.